Species of Lilium have become increasingly popular as flowering pot plants and cut flowers. Easter lilies (Lilium longiflorum) have been historically used at Easter and other religious occasions. Cultivars of other Lilium species and hybrids have become even more important in the market place. The so-called Asiatic hybrids and Oriental hybrids, among others, are the most important of these.
Lilies are grown from bulbs which, in nature, typically go through a two to three year growth cycle before they can be induced to flower. The forcing procedure usually involves a low temperature vernalization treatment which induces flower initiation. Easter lilies, in general, are forced to flower once each year for the Easter holiday. Asiatic, Oriental, and other lilies are forced to flower year-round. In order to achieve year-round flowering, bulbs are vernalized and then frozen until needed. The longer the period of time that the bulbs are frozen, the lower is the number of flowers per bulb.
Recently developed methodologies have enabled growers to shorten the growth period and to eliminate the vernalization treatment necessary before forcing for flowering, particularly for certain cultivars of Lilium longiflorum. Oglevee et al. describe the growth of Easter lilies in one year or less (U.S. Pat. No. 4,570,379, issued 2/18/86 to James R. Oglevee, James F. Tammen, and Wendy O. O'Donovan). The Oglevee patent describes a procedure whereby a leaf from a substantially pathogen-free lily plant is propagated in a growing medium to form a bulblet which is thereafter grown in plant form rather than bulb form. The plant is initially grown under short days to prevent flowering; then flowers are initiated through growth under long day conditions.
Unlike the subject invention, the Oglevee patent pertains primarily to the production of plants rather than bulbs. Furthermore, unlike the subject invention, Oglevee does not utilize tissue culture techniques. Tissue culture techniques facilitate the production of a large number of plants which do not exhibit phenotypic variation. Also, Oglevee does not recognize or utilize the temperature sensitivity of the Lilium bulbs or plants, nor does it involve the use of temperature and light equations to regulate growth in order to enhance the quality of the flowers and to flower lilies year-round.